Method and device for adapting a characteristic variable of a vehicle, vehicle, computer program product and computer-readable storage medium

Abstract

In a method for adapting a characteristic variable of a vehicle, the vehicle having an exhaust gas sensor, an exhaust gas sensor signal of the exhaust gas sensor is received. A characteristic variable which is representative of a combustion air ratio of the vehicle is determined in dependence on the exhaust gas sensor signal. In dependence on the characteristic variable, it is determined whether a transition from a superstoichiometric air-fuel mixture to a substoichiometric air-fuel mixture or a transition from a substoichiometric air-fuel mixture to a superstoichiometric air-fuel mixture is imminent. If a transition is imminent, a current value of the characteristic variable is adapted until a predefined termination condition is met. The actual value of the characteristic variable is transmitted.

Description

[0001] 202401163

[0002] 1

[0003] Description

[0004] Method and apparatus for adjusting a characteristic parameter of a vehicle, vehicle, computer program product and computer-readable storage medium

[0005] A method for adjusting a vehicle characteristic is described. Furthermore, a device for adjusting a vehicle characteristic is described. Finally, a vehicle is described.

[0006] Furthermore, a computer program is specified. Additionally, a computer-readable storage medium is specified.

[0007] Many vehicles are equipped with a catalytic converter, particularly a three-way catalytic converter. These vehicles also have one or more nitrogen oxide sensors, so-called NOx sensors. EU7 legislation makes it mandatory to measure and determine a vehicle's NOx emissions using an in-vehicle NOx sensor. Since an NOx sensor based on the amperometric measurement principle measures the sum of nitrogen oxides (NOx) and ammonia (NH3) concentration in the exhaust gas, as it is cross-sensitive to NH3, it is necessary to separate the NOx and NH3 components from the measured total signal.

[0008] One task to be solved is to contribute to reliably determining a characteristic parameter of a vehicle's exhaust gas.

[0009] This task is solved by the method and the subject matter of the independent patent claims. Advantageous embodiments, implementations, and further developments are the subject of the respective dependent patent claims.

[0010] First, the procedure for adjusting a vehicle parameter is explained. The vehicle has an exhaust gas sensor designed to provide a signal representative of the oxygen content in the exhaust gas. 202401163

[0011] 2

[0012] The exhaust gas sensor is, for example, a lambda sensor and / or a nitrogen oxide sensor. The nitrogen oxide sensor can also be called a NOx sensor and is based in particular on the amperometric measurement principle.

[0013] The exhaust gas sensor is typically located downstream of a three-way catalytic converter. Alternatively, the exhaust gas sensor is located upstream of the three-way catalytic converter.

[0014] The process involves receiving an exhaust gas sensor signal.

[0015] Depending on the exhaust gas sensor signal, a characteristic value is determined that is representative of the combustion air ratio of the vehicle.

[0016] The parameter is, for example, representative of a linear lambda signal.

[0017] As an alternative to the linear lambda signal, any other signal representative of the oxygen content or lambda value of the exhaust gas can be used. Examples include a binary lambda signal (measured in volts) or an oxygen concentration (measured in ppm or %). Here, lambda specifically represents the air-fuel ratio compared to a stoichiometric combustion mixture.

[0018] The exhaust gas sensor signal is a related signal, i.e., a binary lambda signal and / or a linear lambda signal and / or an oxygen concentration signal.

[0019] Depending on the parameter, it is determined whether a transition from a superstoichiometric air-fuel mixture to a substoichiometric air-fuel mixture or a transition from a substoichiometric air-fuel mixture to a superstoichiometric air-fuel mixture is imminent.

[0020] If a transition is imminent, the current value of the parameter is adjusted until a predefined termination condition is met. 202401163

[0021] 3

[0022] The current value of the parameter is sent, particularly for further processing.

[0023] Depending on the transmitted value of the parameter, the vehicle's engine control can then be adjusted and / or it can be determined whether a measurement signal from a nitrogen oxide sensor is representative of nitrogen oxides or ammonia.

[0024] In general, the following relationship applies between the emissions downstream of a three-way catalyst and the lambda condition of the three-way catalyst or downstream of the three-way catalyst:

[0025] When operating the catalytic converter with a superstoichiometric air-fuel mixture (lambda > 1, so-called "lean operation" or "lean mixture"), not all nitrogen oxides from combustion can be broken down, as the required reducing agent (e.g., CO) has already been oxidized beforehand. As a result, a certain concentration of NOx is present downstream of the catalytic converter, which can be detected by a nitrogen oxide sensor. The nitrogen oxide sensor can also be referred to as a NOx sensor. NOx is used here as a synonym for nitrogen oxides and is a collective term for gaseous oxides of nitrogen, especially nitric oxide (NO) and nitrogen dioxide (NO2).

[0026] If the catalyst is operated with a substoichiometric air-fuel mixture (lambda < 1 , so-called “rich operation” or “rich mixture”), not all hydrocarbons and carbon monoxide present can be broken down.

[0027] Additionally, ammonia (NH3) is produced as a side reaction during this rich-fuel operation, resulting in another pollutant. Consequently, the nitrogen oxide sensor downstream of the catalytic converter measures a certain concentration of NH3. However, all NOx emissions are converted to N2 and CO2 because sufficient rich gases (CO) are present. Therefore, only NH3 exists downstream of the catalytic converter, and no NOx remains. 202401163

[0028] 4

[0029] However, this simple approach to distinguishing between NOx and NH3 emissions does not allow for a correct separation between NOx and NH3 under all conditions.

[0030] During steep transitions with a lambda value of 1000 (especially from rich to lean), exhaust gas sensors experience a brief and steep drop in the linear lambda signal due to their control system. This drop is caused by the sensor's pump control and therefore does not represent a true lambda value decrease. This drop is also visible in a measured oxygen signal. Similarly, the signal can also be positive when transitioning from lean to rich.

[0031] This negative (or positive) deflection in the respective signal can lead to the engine's lambda control mistakenly reacting to the supposed drop (or rise) into rich (or lean) with a countermeasure during engine operation, or to a NOx-NH3 separation algorithm incorrectly recognizing NH3 when the deflection is into rich (or NOx when the deflection is into lean).

[0032] To avoid such erroneous reactions to the lambda reading, this method discloses a measure that filters out such lambda readings. According to the method, an adjusted lambda value or an adjusted oxygen value is used instead of the measured signal until the aforementioned measurement error has ceased.

[0033] Thus, the method allows for a reliable determination of lambda and its use for engine operation or a NOx-NH3 separation algorithm.

[0034] According to one embodiment of the method, the parameter is extrapolated several time steps into the future, and depending on the extrapolation, it is determined whether the transition is imminent. 202401163

[0035] 5

[0036] Extrapolation into the future can be based on the linear or binary lambda signal or the oxygen signal. For exhaust gas sensors that can measure both a linear and a binary lambda signal, both signals can be used, or optionally just one. Using a binary lambda signal for extrapolation is advantageous because it is not distorted by a faulty signal deflection during the lambda = 1 reading and exhibits very high sensitivity in the region around lambda = 1.

[0037] Extrapolation in this context means that an estimate of the lambda value is made several time steps into the future (for example, about 200-300 ms). The procedure might look something like this:

[0038] First, a lambda gradient is calculated from the current lambda value at time ii and a lambda value from the past at time ii-x. Here, x is the number of data points one wants to look back at. For example, 1-3 data points are chosen, which corresponds to 100-300 ms with a sampling time of 100 ms.

[0039] The calculated lambda gradient is then extrapolated into the future to predict the lambda value that will be present in y samples if the current lambda gradient persists. For example, the extrapolation length might be 200-300 ms (or 2-3 samples at a 100 ms sampling rate). Based on the extrapolated lambda, a lambda = 1 passage detection can then be performed.

[0040] The passage can be determined using the following criteria. In particular, all must be active; for example, from fat to lean, the reverse criteria apply for lean to fat:

[0041] -Lambda was rich at the last time point. This can be detected, for example, using a linear lambda signal (lambda < 1) or a binary lambda signal (e.g., lambda > 500 mV if the jump point is at 500 mV). The jump point is a characteristic parameter of a binary probe and depends on the sensor characteristics of the respective sensor. 202401163

[0042] 6

[0043] -Extrapolated lambda exceeds or falls below the lambda = 1 point (linear lambda: lambda value > 1 , binary lambda: lambda value < 500 mV).

[0044] The lambda signal continues to rise or fall in the direction of lambda = 1 pass, thus exhibiting a positive or negative gradient.

[0045] Alternatively or additionally, two nitrogen oxide sensors and / or lambda sensors can be used to determine whether a transition is imminent: one downstream of the catalyst and one upstream. If a lambda signal from the upstream sensor reaches a lambda = 1 transition, the downstream transition must also occur promptly.

[0046] According to one embodiment of the method, the current value of the parameter is representative of a linear lambda signal and the current value of the parameter is adjusted by further extending the linear lambda signal towards lambda = 1 with a predetermined filter constant, whereby a maximum or minimum from the current value of the parameter without adjustment and lambda = 1 is taken as the target value.

[0047] This adjustment can also be called filtering. For example, when a lambda = 1 crossing is detected, the filtering of a linear lambda signal proceeds as follows: the linear lambda signal continues towards lambda = 1 with a predefined filter constant. The target value is the maximum of the actual lambda value and lambda = 1.000. This ensures that filtering always occurs towards lambda = 1.000. However, if the actual unfiltered lambda value (=Ai i-1) is already greater than 1.000 (because the negative peak has already passed), filtering continues towards the actual lambda value until the termination criterion for the lambda = 1 crossing is met. The same applies in the other direction.

[0048] Similar filtering methods that suppress changes in the direction of the lambda signal are also possible. 202401163

[0049] 7

[0050] According to one embodiment of the method, the specified termination condition includes the requirement that a current value of the parameter without adjustment is representative of the fact that the transition from a superstoichiometric air-fuel mixture to a substoichiometric air-fuel mixture or the transition from a substoichiometric air-fuel mixture to a superstoichiometric air-fuel mixture has occurred, e.g., if the lambda value without adjustment is > 1.01 during the transition from a substoichiometric air-fuel mixture to a superstoichiometric air-fuel mixture.

[0051] In other words, the adjustment remains active until the value of the parameter has completed the Lambda = 1 cycle.

[0052] Alternatively or additionally, the following termination conditions can be used:

[0053] According to one embodiment of the method, the specified termination condition includes that the adjusted value of the parameter has reached a maximum or minimum of the current lambda value without adjustment and lambda = 1.

[0054] According to one embodiment of the method, the specified termination condition includes the gradient of a binary lambda signal changing its sign.

[0055] In other words, the adjustment remains active as long as the binary lambda signal is still moving towards lean (gradient < 0), or as long as the binary lambda signal is still moving towards rich (gradient > 0).

[0056] The invention is further characterized by a device, wherein the device is configured to carry out the described method or an embodiment of the method. 202401163

[0057] 8

[0058] The invention is further characterized by the device comprising a vehicle.

[0059] Furthermore, a computer program product is specified, comprising instructions which, when the computer program is executed by a computer, cause it to perform the procedure described herein.

[0060] Furthermore, a computer-readable storage medium is specified on which the computer program described here is stored.

[0061] Exemplary embodiments of the invention are explained in more detail below with reference to the schematic drawings.

[0062] They show:

[0063] Figure 1 shows a flowchart of a program for adjusting a characteristic parameter of a vehicle and

[0064] Figure 2 shows an exemplary curve of a measured lambda signal and a fitted lambda signal.

[0065] Figure 1 shows a flowchart of a program for adjusting a characteristic parameter of a vehicle.

[0066] The vehicle has one or more exhaust gas sensors. One exhaust gas sensor is located, in particular, downstream of a three-way catalytic converter. Another is located, for example, upstream of the three-way catalytic converter. The respective exhaust gas sensor is, for example, a lambda sensor and / or a nitrogen oxide sensor. The nitrogen oxide sensor can also be referred to as a NOx sensor and is based, in particular, on the amperometric measuring principle.

[0067] The procedure can be carried out, for example, by means of a control device 10. 202401163

[0068] 9

[0069] The control device 10 comprises, in particular, a processing unit, a program and data memory, and, for example, one or more communication interfaces. The program and data memory and / or the processing unit and / or the communication interfaces can be integrated into a single unit and / or distributed across multiple units. The control device 10 is, in particular, coupled to the exhaust gas sensor and the three-way catalytic converter for receiving measurement data from the exhaust gas sensor and / or the three-way catalytic converter.

[0070] The control device 10 can also be described as a device for adjusting a characteristic value.

[0071] The program is stored in particular on the program and data memory of the control device 10.

[0072] The program is started in step S1, in which variables can be initialized if necessary.

[0073] In step S3, an exhaust gas sensor signal is received. The exhaust gas sensor is specifically the exhaust gas sensor downstream of the three-way catalytic converter and / or the exhaust gas sensor upstream of the three-way catalytic converter.

[0074] The exhaust gas sensor signal is particularly representative of a binary lambda signal and / or a linear lambda signal and / or an oxygen concentration signal.

[0075] The exhaust gas sensor signal is optionally filtered to minimize noise.

[0076] In step S5, a parameter is determined that is representative of the vehicle's air-fuel ratio. 202401163

[0077] 10

[0078] This parameter is representative, for example, of a linear lambda signal. Alternatively, any other signal representative of the oxygen content or lambda value of the exhaust gas can be used. Examples include a binary lambda signal (measured in volts) or an oxygen concentration (measured in ppm or %). Here, lambda specifically represents the air-fuel ratio compared to a stoichiometric combustion mixture.

[0079] In step S7, depending on the parameter, it is determined whether a transition from a superstoichiometric air-fuel mixture to a substoichiometric air-fuel mixture or a transition from a substoichiometric air-fuel mixture to a superstoichiometric air-fuel mixture is imminent.

[0080] To determine the transition, for example, an extrapolation of the parameter several time steps into the future is carried out, and depending on the extrapolation, it is determined whether the transition is imminent.

[0081] Extrapolation into the future can be based on the linear or binary lambda signal or the oxygen signal. For exhaust gas sensors that can measure both a linear and a binary lambda signal, both signals can be used, or optionally just one. Using a binary lambda signal for extrapolation is advantageous because it is not distorted by a faulty signal deflection during the lambda = 1 reading and exhibits very high sensitivity in the region around lambda = 1.

[0082] Extrapolation in this context means that an estimate of the parameter is made several time steps into the future (for example, approximately 200-300 ms). The procedure might look like this:

[0083] First, a lambda gradient is calculated from the current lambda value at time ii and a lambda value from the past at time ii-x. Here, x is the number of data points to include in the calculation.

[0084] 11

[0085] who wants to look at the past. For example, 1-3 data points are selected, which corresponds to 100-300 ms with a sampling time of 100 ms.

[0086] The calculated lambda gradient is then extrapolated into the future to predict the lambda value that will be present in y samples if the current lambda gradient persists. For example, the extrapolation length is 200-300 ms (or 2-3 samples at a 100 ms sampling rate). Based on the extrapolated lambda, a lambda = 1 passage detection can now be performed.

[0087] The passage can be determined using the following criteria. In particular, all must be active; for example, from fat to lean, the reverse criteria apply for lean to fat:

[0088] -Lambda indicates a rich mixture at the last time point. This can be detected, for example, using a linear lambda signal (lambda < ) or a binary lambda signal (e.g., lambda > 500 mV if the jump point is at 500 mV). The jump point is a characteristic parameter of a binary probe and depends on the sensor characteristics of the respective sensor.

[0089] -Extrapolated lambda exceeds or falls below the lambda = 1 point (linear lambda: lambda value > 1 , binary lambda: lambda value < 500 mV).

[0090] The lambda signal continues to rise or fall in the direction of lambda = 1 pass, thus exhibiting a positive or negative gradient.

[0091] Alternatively or additionally, two nitrogen oxide sensors and / or lambda sensors can be used to determine whether a transition is imminent: one downstream of the catalyst and one upstream. If a lambda signal from the upstream sensor reaches a lambda = 1 transition, the downstream transition must also occur promptly.

[0092] In step S9, if a transition is imminent, a current value of the parameter is adjusted until a predefined termination condition is met.

[0093] The adjustment is made, for example, as follows: 202401163

[0094] 12

[0095] For example, the current value of the parameter is representative of a linear lambda signal, and the current value of the parameter is adjusted by further adjusting the linear lambda signal towards lambda = 1 with a predefined filter constant, whereby a maximum or minimum from the current value of the parameter without adjustment and lambda = 1 is taken as the target value.

[0096] This adjustment can also be called filtering. For example, when a lambda = 1 crossing is detected, the filtering of a linear lambda signal proceeds as follows: the linear lambda signal continues towards lambda = 1 with a predefined filter constant. The target value is the maximum of the actual lambda value and lambda = 1.000. This ensures that filtering always occurs towards lambda = 1.000. However, if the actual unfiltered lambda value (=Ai i-1) is already greater than 1.000 (because the negative peak has already passed), filtering continues towards the actual lambda value until the termination criterion for the lambda = 1 crossing is met. The same applies in the other direction.

[0097] Similar filtering methods that suppress a change in the direction of the lambda signal are also possible.

[0098] One or more of the following termination conditions can be used:

[0099] - A current value of the parameter without adjustment is representative of the fact that the transition from a superstoichiometric air-fuel mixture to a substoichiometric air-fuel mixture or the transition from a substoichiometric air-fuel mixture to a superstoichiometric air-fuel mixture has occurred, e.g., if the lambda value without adjustment is > 1.01 during the transition from a substoichiometric air-fuel mixture to a superstoichiometric air-fuel mixture. In other words, 202401163

[0100] 13. The adjustment remains active until the measured lambda value has completed the lambda = 1 cycle;

[0101] - the adjusted value of the parameter reaches a maximum or minimum from the current lambda value without adjustment and lambda = 1 ;

[0102] - The gradient of a binary lambda signal changes sign. In other words, the adjustment remains active as long as the binary lambda signal still points towards lean (gradient < 0), or as long as the binary lambda signal still points towards rich (gradient > 0).

[0103] In step S11, the current value of the parameter is transmitted. Subsequently, depending on the transmitted value, the vehicle's engine control is adjusted. Alternatively or additionally, depending on the transmitted value, it is determined whether a measurement signal from a nitrogen oxide sensor is representative of nitrogen oxides or ammonia.

[0104] In step S13, the program is terminated and can be restarted in step S1 if necessary.

[0105] Figure 2 shows an example of a measured lambda signal and a fitted lambda signal.

[0106] As can be seen, due to the control system, a short and steep drop in the measured lambda value occurs during the course of a measured linear lambda signal 20. This drop is caused by the sensor's pump control and therefore does not represent a true lambda drop, but rather a measurement error. Similarly, the signal deflection can also be in the positive direction when the mixture changes from lean to rich.

[0107] The corrected lambda value, adjusted using the program described above, does not show such a drop as in the course of the adjusted lambda signal 30 202401163

[0108] 14 can be seen, thus enabling reliable engine control and / or a reliable NOx-NH3 separation algorithm.

[0109] Furthermore, the corresponding course of a binary lambda signal 40 can be seen with a characteristic jump at the lambda = 1 transition.

[0110] 202401163

[0111] 15

[0112] Reference symbol list

[0113] S1-S 13 steps

[0114] 10 Control device 20 Course of a measured lambda signal

[0115] 30. Course of a fitted lambda signal

[0116] 40. Course of a binary lambda signal

Claims

202401163 16 Patent claims 1. Method for adjusting a characteristic parameter of a vehicle, wherein the vehicle has an exhaust gas sensor, wherein in the method an exhaust gas sensor signal is received, a characteristic parameter is determined depending on the exhaust gas sensor signal which is representative of a combustion air ratio of the vehicle, depending on the characteristic parameter it is determined whether a transition from a superstoichiometric air-fuel mixture to a substoichiometric air-fuel mixture or a transition from a substoichiometric air-fuel mixture to a superstoichiometric air-fuel mixture is imminent, if a transition is imminent, a current value of the characteristic parameter is adjusted until a predetermined termination condition is met, and the current value of the characteristic parameter is transmitted.

2. Method according to claim 1, wherein an extrapolation of the parameter is performed several time steps into the future and, depending on the extrapolation, it is determined whether the transition is imminent.

3. Method according to one of the preceding claims, wherein the current value of the characteristic parameter is representative of a linear lambda signal and wherein the current value of the characteristic parameter is adjusted by further adjusting the linear lambda signal with a predetermined filter constant towards lambda = 1, wherein the target value is a maximum or minimum derived from the current value of the characteristic parameter without adjustment and lambda = 1.

4. A method according to any of the preceding claims, wherein the predetermined termination condition comprises that a current value of the characteristic without adjustment is representative of the fact that the transition from a superstoichiometric air-fuel mixture to a substoichiometric air-fuel mixture or the transition from a substoichiometric 202401163 17 The air-fuel mixture has become a superstoichiometric air-fuel mixture.

5. Method according to one of the preceding claims, wherein the specified termination condition comprises that the adjusted value of the parameter has reached a maximum or minimum of the current parameter without adjustment and Lambda = 1.

6. Method according to any of the preceding claims, wherein the specified termination condition comprises that a gradient of a binary lambda signal changes sign.

7. Device, wherein the device is configured to perform the method according to any of the preceding claims.

8. Vehicle comprising the device according to claim 7.

9. Computer program product comprising instructions which, when the program is executed by a computer, cause it to execute the method according to any one of claims 1 to 6.

10. Computer-readable storage medium comprising instructions which, when executed by a computer, cause the computer to execute the method according to any one of claims 1 to 6.

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